Method for repairing craters in the surface of a concrete runway

ABSTRACT

A cylindrical rubber drum containing a &#39;&#39;&#39;&#39;fast fix&#39;&#39;&#39;&#39; cement and water in proper proportion and having metal ends for receiving ball bearings. A stationary shaft passes through the drum and a towing hitch is applied to the shaft. An inert gas is introduced into the drum either from a tank under pressure or by encapsulation to take up the ullage space caused by the shrinkage of the concrete mix. Paddles are mounted on the shaft so that as the drum is towed at a fast clip toward a damaged runway, the mixture is churned into a slurry of proper consistency and can be used immediately in leveling and hardening the fill which has previously been dumped into the crater.

United States Patent 1 Stevenson METHOD FOR REPAIRING CRATERS IN THE SURFACE OF A CONCRETE RUNWAY Karl F. Stevenson, 19 Oakdale Road N.W., Fort Walton Beach, Fla.

Filed: Feb. 12, 1971 Appl. No.: 114,854

Inventor:

Related U.S. Application Data Division of Ser. No. 853,872, Aug. 28, 1969, Pat. No. 3,592,448.

References Cited UNITED STATES PATENTS 4/1941 Hackley ..259/151 8/1964 Retzlaff ..259/l76 [451 Feb. 20, 1973 3,473,789 10/1969 Dietrich ..259 175 3,232,586 2/1966 McClive ..259/177R Primary Examiner-Robert W. Jenkins Att0rneyHarry A. Herbert, Jr. and Richard J. Kilioren ABSTRACT A cylindrical rubber drum containing a fast fix" cement and water in proper proportion and having metal ends for receiving ball bearings. A stationary shaft passes through the drum and a towing hitch is applied to the shaft. An inert gas is introduced into the drum either from a tank under pressure or by encapsulation to take up the ullage space caused by the shrinkage of the concrete mix, Paddles are mounted on the shaft so that as the drum is towed at a fast clip toward a damaged runway, the mixture is churned into a slurry of proper consistency and can be used immediately in leveling and hardening the till which has previously been dumped into the crater.

1 Claim, 6 Drawing Figures III] PATENIE riazoms 3,717,328 SHEET 30F 4 METHOD FOR REPAIRING CRATERS IN THE SURFACE OF A CONCRETE RUNWAY REFERENCE TO RELATED PATENT APPLICATION This is a division of application GROUND ACTU- ATED DRUM FOR MAKING BATCH OF CONCRETE SLURRY, Ser. No. 853,872, filed Aug. 28, 1969 now U.S. Pat. No. 3,592,448.

BACKGROUND OF THE INVENTION In times of war, a bomb crater hole on the active surface of a runway over which heavy planes travel may prove disastrous. It is imperative that the crater be repaired including the laying down of a cap of cement within an extremely short time after the crater has been formed.

Heretofore, it has been the practice to rush a rotary concrete mixer to the scene together with a dump truck or two carrying the fill material, also the required amount of concrete and water. The trucks usually waste very little time in dumping the necessary amount of fill into the crater hole. But even though the concrete mixing operation using a standard machine was started immediately, there is a considerable waiting period before the slurry has attained the proper consistency to be poured. Considering the urgency of the situation, this waiting period can ill be afforded, particularly when an additional period must be allowed for the cement to harden sufficiently to support the weight of a heavy bomber.

SUMMARY OF THE INVENTION An object of the invention is to provide an improved structure by which the concrete mixing at the site of the crater can be dispensed with and concrete in slurry form can be made instantly available at the scene of the crater.

Another object is to provide an improved method of patching bomb craters in the shortest period of time, and one which eliminates the use of a rotary cement mixer and the waiting period that a machine of this type entails. These objects are obtained in brief by bringing together, at the point of supply, the required quantity of concrete and water within a round drum structure which, upon being pulled over the ground toward the repair job, sets up shear forces within the drum which changes the mixture into a slurry of fine texture, ready to be used at the crater.

Other objects and features will be apparent as the specification is perused in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 diagrammatically represents a crater formed in a runway after having been struck with a bomb.

FIG. 2 is a similar view but showing the manner in which the crater has been filled and then capped by a concrete slab in order to retain a smooth surface throughout its length.

FIG. 3 shows in cross section, a barrel or drum of the improved travelling mixer having a shaft shown in elevation together with a tow hitch broken away to conserve space.

FIG. 4 represents a sectional view taken along line 4-4 in FIG. 3 and looking in the direction of the arrows.

FIG. 5 shows a plan view looking down on top of the barrel or drum shown in FIG. 3.

FIG. 6 is a fragmentary view of a modified form of the improved mixer. Only the end portions of the mixer are illustrated and these are in section. The central shaft is shown in elevation and the hitch device is merely indicated.

Referring to FIGS. 1 and 2, reference character 1 designates an active runway forming one unit of a pair and assuming that the plane would travel from left to right over the runway if the latter had been in good condition. However, a bomb has hit the runway and has formed roughly a hemispherical crater 2, throwing the usual debris 3 about the edge of the crater. The runway together with its companion strip may be used by heavy bombers for takeoff and landing, perhaps to and from enemy terrain so that it is absolutely necessary that the crater be filled and the concrete cap applied in the shortest period of time.

Whereas, heretofore it has been the custom to dispatch a cement mixer as quickly as possible to the scene, followed by a truck carrying cement and water, and perhaps a second truck with fill dirt or gravel. However, a conventional mechanical proportional mixer capable of fulfilling the stated requirements would have the same size and involve the same amount of mechanical equipment as would be needed for repairing a relatively small rocket crater as for repairing a large bomb crater. In accordance with one aspect of my invention, I employ a drum or barrel which can be used for cement storage, and when a patching effect is necessary on an emergency basis, water is added to the concrete and the barrel is caused to roll along the ground, as when being pulled by a fast moving vehicle, in the direction of the crater. By the time the latter is reached, the concrete is in perfect slurry form and contains no more and no less than the required amount of concrete for the particular job at hand. It is apparent that the barrel or drum becomes its own mixer and furnishes the transportation for the slurry. Assuming that an estimate of the amount of the slurry necessary having been previously made, one or more drums containing the slurry material can be dispatched as a tandem arrangement and pulled by the same vehicle.

FIG. 3 shows one form that the combined slurry mixer and transportation unit may take. Reference character 4 designates a sealed drum made of rubber, preferably reinforced by fiber and of substantial thickness. The drum is normally closed except at the ends to which is affixed a pair of aluminum plates 5. The latter carry a set of ball bearings 6 and a shaft 7. In order to effect a seal between the end walls of the drum and the plates, the wall of the drum may be made thinner as at 8 and this thinned portion can be snubbed into a circumferential groove formed in the plate 5. A number of equidistantly spaced bolts 9 pass through the end plate and clamp the rubber portions within the grooves and thereby obtain an air and water tight seal. The shaft 7 is freely rotatable with respect to the drum 4 and, as shown, extends for a considerable distance at each end beyond the ball bearings. These end portions of the shaft have a key slot 10, the purpose of which will be described hereinafter. There are a number of flat paddle members 11 of which 11 have been illustrated, and these members are equally spaced along the shaft as shown in FIG. 3. They are of the same radial length and radiate at equal angles from the shaft as indicated in FIG. 4. The paddles may be welded or otherwise secured to the shaft.

The drum 4 has a large rectangular opening 12 having a stepped edge 13 about its periphery for receiving a plate of rubber 14. The latter has a peripheral edge that fits snugly within the opening 12. A rectangular metal member 15 of dished shape, when looking directly into FIG. 3, and of arcuate shape as viewed in a direction at right angles thereto, is molded at the edges 16 into the peripheral body of the drum. Six flat headed screws 17 pass through the plate member 14, and are threaded into openings in the metal member 15 to hold the plate member 14 firmly in place. The metal member 15 has a large rectangular opening 18 leading to the interior of the drum.

It is obvious by disconnecting the screws 17 from the plate 15, the plate 14 can be removed to leave a large opening at the top of the drum for receiving concrete in dry form as will be described hereinafter.

In order to tow the drum over the ground, a hitch designated generally at 22 is provided, formed as an A- frame out of aluminum pipe. A brace bar 23 is welded to the outer legs 24 and each of the latter terminate in a collar 25. The latter has an opening slightly larger than the shaft, and as shown, is keyed as indicated at 26 to the shaft. Cotter pins 27, backed-up by a washer, pass through the shaft to prevent the collars 25 from moving along the shaft. The forward end of the hitch is bent inwardly as indicated at 28 and terminates in a portion having an opening 29 for receiving the tow bar of a truck.

It will be noted that the shaft 7 extends for a distance outwardly beyond the collars 25. This added length of shaft is for the purpose of receiving the end collars of a tow structure or hitch (not shown) for pulling a second drum, similar to drum 4, in the event that a greater amount of concrete slurry is required than can be accommodated by a single unit. Any number of drums may be pulled tandem fashion.

In practice, the drums are filled to capacity with a suitable concrete by removing the plate 14 as described hereinbefore. While any highly refined perfectly dry cement may be used, I have received particularly good results by employing a special form of cement, sold under the name of Fast-Mix cement. This cement is made and marketed by the Western Company, Richardson, Tex. It is known for having a heavy creamlike consistency which percolates through a gravel substructure to form a structural section. When a strike on a runway, by an enemy bomb, has been reported, the officer dispatches the necessary fill dirt and/or gravel together with sufficient help to clean all the loose debris usually found around the perimeter of a crater. Simultaneously with this action, an estimate is made as to the quantity of concrete that must be poured over the fill to allow the formation of a final smooth cap. The latter is usually about 1 inch thick. The quantity of cement required is translated into the number of drums. Water is immediately added in the proper amount by unscrewing the cap 21. The concrete and water when mixed is automatically reduced in volume and this fact may leave a temporary vacuum within the space not occupied by the mixture. This in turn could cause a distortion of the rubber due to the flattening of the drum at the bottom as it is hauled over the ground. It is therefore desirable to introduce into the drum a dry gas such as carbon dioxide or nitrogen to serve as ullage and thus maintain the circularity of the drum during the rolling operation. The gas could be introduced in encapsulated form in any suitable and wellknown manner, and it could be applied, if desired, through the water opening 19 from a suitable tank under pressure. The fact that the drum turns but the shaft and paddles remain stationary, due to the anchoring key in the slot 10, will cause the paddles to provide powerful shearing efiects in a number of places on the column of concrete and water within the drum. The result is that a thorough mix is obtained even during a relatively short run to the crater scene. The concrete slurry can be pumped or dumped through the opening 12, when the plate 14 is removed, on top of the gravel fill. Several drums forming a tandem group may be required if the crater is large and attendant help can then smooth out the upper portion of the cement to form the proper thickness of cap.

While I have shown and described the use of paddle elements secured to the shaft, for mixing the concrete, other forms of churning devices might be used to advantage, such as loose metal cables strung across the metal end walls of the drum. A flat metal band in the form of a helix or spiral could also be welded to the shaft at suitable crossing points to provide a traveling screw effect. If desired, the inside surface of the drum may be provided with deep corrugations or steep radially extending projections moulded into the rubber in order to assure a good mixing effect.

In FIG. 6, there is shown a modified form of the traveling mixer. The same reference characters designate similar elements shown in FIG. 3. In FIG. 6, the drum 4 is provided with shorter inwardly extending legs than in FIG. 3 and are further provided with thinned portions 8 which can be snubbed into sealing position within a groove formed in the periphery of relatively large plates 30 at each end of the drum. The plates 30 are preferably made of aluminum. The righthand plate, as seen in the figure, has a large circular opening 31 having a stepped periphery for receiving the screw threads 32 of a circular plate 33 made of aluminum and having a hexagon head 34. Thus, by unscrewing the member 33 and withdrawing the same, the opening 31 is exposed for filling the drum 4 with concrete, preferably of the kind heretofore set forth. It will be understood that the opening 31 takes the place of the opening 18 in FIG. 3 so that the drum 4 in FIG. 6 is devoid of the elements 14, 15 and 17 of FIG. 3. The end plate 30 is provided with a set of ball bearings 6 which freely permits the drum 4 to rotate with respect to the shaft 7.

At the left hand end of the drum, as seen in FIG. 6, there is a smaller circular opening 35 in the end plate 30. This opening is closed by a threaded plate member having a hexagon head 36. The opening is provided for the purpose of introducing the necessary amount of water into the interior of the drum. This end plate, similar to the opposite end, is provided with a set of ball-bearings 6 for rotatably receiving the shaft 7. As in the case of the structure described in connection with FIG. 3, the modified form of drum mixer can be pro vided with paddles welded to the shaft or any other form of agitating device as will produce the necessary shear forces on the concrete-water mix when the drum is hauled over the ground.

FIG. 6 also shows an inflation valve 37 of any suitable and well-known type for introducing air or gas, when desired, into the drum. The valve includes a threaded stem 38 which enters one of the side plates 30 and contains a spring-pressed head 40 which bears against a seat 41. The valve is controlled by a long pin 42 which is made accessible for pressing inward when the cap 43 is removed. The valve can be used for a three-fold purpose:

1. To introduce dry air or nitrogen to keep the charge of concrete dry during a storage period, i.e., before an emergency has arisen;

2. To inflate the drum by air or nitrogen after water has been introduced at the opening 35 during an emergency run, to take up the ullage space caused by the mixing of concrete and water; and

3. Introducing air under pressure at the site of the crater to assist in expelling the concrete slurry through the opening 31 which can serve as an exit.

In the opposite side plate 30, there is an opening fitted with a sleeve 43' for carrying a round pipe 44 of metal which can be employed as an exhaust accessory when connected to a suction pump for removing the concrete slurry at a fast rate. The pipe 44 may, if desired, be flattened to present a wider opening, as indicated at 45, in order to hug and conform to the inside surface of the drum at the bottom. In this manner, the maximum amount of slurry can be evacuated.

For pulling the drum toward the crater, a hitch, generally indicated at 22, is employed having collars which are keyed to the shaft 7. Thus, the shaft and any agitating device connected thereto remain stationary as the drum moves over the ground, and a strong churning or mixing effect is introduced within the drum. The shaft 7 is extended beyond the collars to receive, if desired, similar collars of a hitch connected to a second drum, tandem fashion, as many as are necessary for the job at hand.

From the foregoing, it is evident that there is disclosed an improved combined storage device for dry concrete and a fast mixer, when necessary, to supply slurry almost on an instant notice, in any amount necessary, and available at the site of a damaged runway. No mixing machine is necessary as the slurry is produced solely within the improved device during the hauling operation toward the damaged structure.

I claim:

1. In the art of maintaining concrete runways free from holes and craters in the surface, comprising: making available a number of rubber drums filled with concrete in dry form within a relatively short distance from the runway wherein a hole or crater may be formed; introducing water into as many drums as will furnish the necessary slurry when mixed with the concrete to complete the repair job; introducing into the drums a quantity of dry gas to take up the ullage space in each drum caused by the shrinkage in volume of the concrete and water whereby the circularity of the drum IS maintained during a hauling process;

pulling the drums over the ground in the direction of the repair scene in order to agitate the concrete and water mix into a slurry of predetermined consistency ready to be applied to the crater in the damaged runway and supplying air under pressure to the drum, at the crater sight, to aid in expelling the slurry from the drum through an opening in the drum. 

1. In the art of maintaining concrete runways free from holes and craters in the surface, comprising: making available a number of rubber drums filled with concrete in dry form within a relatively short distance from the runway wherein a hole or crater may be formed; introducing water into as many drums as will furnish the necessary slurry when mixed with the concrete to complete the repair job; introducing into the drums a quantity of dry gas to take up the ullage space in each drum caused by the shrinkage in volume of the concrete and water whereby the circularity of the drum is maintained during a hauling process; pulling the drums over the ground in the direction of the repair scene in order to agitate the concrete and water mix into a slurry of predetermined consistency ready to be applied to the crater in the damaged runway and supplying air under pressure to the drum, at the crater sight, to aid in expelling the slurry from the drum through an opening in the drum. 